As is well known, when an internal combustion engine is to be started, the engine crankshaft is rotated by the force of an electric motor while an air/fuel mixture is supplied to cylinders of the engine. For instance, in a fuel injection system the basic amount of fuel supplied to the engine is determined in accordance with the amount of intake air and the engine rpm, i.e. the rotational speed of the crankshaft of the engine. This basic amount of fuel is, however, modified by various engine parameters, such as engine temperature and the amount by which the throttle flap is open.
In order to obtain a smooth engine start, the engine is supplied with a rich mixture during cranking. This operation of supplying a rich mixture into the cylinders of the engine takes place not only in a fuel injection system as well as in a carburetor system. If combustion takes place as soon as cranking starts, the air/fuel mixture supplied to each cylinder of the engine is burnt and normal engine operation stars. However, when misfire occurs and cranking takes place continuously, the combustion chamber(s) is wetted by fuel. Accordingly, the spark plug of each cylinder gets wet, whereby firing of the air/fuel mixture is made more difficult. Since the cranking duration may be lengthened as long as desired by turning on the ignition key, it may be impossible to start the engine, especially in fuel injection systems and electronically controlled carburetor systems having a relatively low air/fuel ratio during cranking.